1. Field of the Invention
The present invention concerns a loading implement, as well as a process for loading implement, with a hydraulic arrangement for raising and lowering a boom.
2. Description of Related Technology
Loading implements are known and include, for example, wheel loaders, telescopic loaders or other construction or agricultural loaders, or even forestry vehicles, that are provided with a hydraulic arrangement for the control of a hydraulic cylinder for lifting and lowering a boom, with which a floating condition of the hydraulic cylinder can be attained. The floating condition may be advantageous if operations are to be performed with the loading implement in which the operating tool is to guide along the surface of the ground as closely as possible to the actual contour of the ground.
An example of such a hydraulic arrangement is disclosed by U.S. Published Application No. US2004/221714 A1. There a hydraulic arrangement for a telescopic loader is provided with a hydraulic cylinder for lifting and lowering a boom and in which a floating condition can be attained. Moreover the hydraulic arrangement is provided with a load holding valve arrangement, as is required for telescopic loaders, in order to protect the boom against a break in the hose or an unintended lowering. To attain a floating condition, hydraulic lines are provided that connect both chambers of a hydraulic cylinder with a hydraulic fluid tank so as to be controlled electronically. Simultaneously the security function of the load holding valve arrangement is maintained.
The disadvantage here is that an activation of the floating condition is possible even if the boom is not located in a position that is supported on the ground. In such a case, the boom would be lowered without any control since the lifting side of the hydraulic cylinder is connected with the hydraulic fluid tank in the floating condition and could possibly inflict damage or sustain damage itself.
The problem underlying the invention is seen in the need to create a loading implement with a hydraulic arrangement for a boom, in which the floating condition can be activated without the boom being lowered uncontrollably.